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Yes that's true Stevie, I hadn't given the throttle deal full consideration honestly, surely the restriction of airflow passed the throttle blade would hurt power though? As opposed to an open throttle with a wastegate controlling boost.
I like the idea of using a BOV to move around on the compressor map, however this sounds like a bandaid for an incorrectly sized turbo.
Yes that's true Stevie, I hadn't given the throttle deal full consideration honestly, surely the restriction of airflow passed the throttle blade would hurt power though? As opposed to an open throttle with a wastegate controlling boost.
I like the idea of using a BOV to move around on the compressor map, however this sounds like a bandaid for an incorrectly sized turbo.
Any leaks on the compressor side create additional exhaust gas pressure. You must have the compressor side sealed up completely, I always boost test the plumbing to whatever pressure I know it will see. The whole plumbing when air tight will actually hold 15-20psi for 20-30 seconds on many setups when sealed up.
Since you're all in though- post your results in a year or the day after never when you get it working.
I call this being an 'askhole'. He won't take in any real science or results, just his own reasoning to support the far fetched idea.
Who is the 'askhole' now?
Throttle plate boost control works. My Turbo Vette has been on the road without a wastegate for over 2 years and over 2 thousand miles now.
Not only does boost control work, I have the ability to set or change boost for any gear or driving mode through my DIY touch screen.
Also boost is momentarily reduced during shifting (while under boost) to reduce transmission wear.
And instead of a rough two step with traditional fuel or spark cut, I can touch screen any boost or RPM for launch control. The engine runs much smoother with this type of launch control.
Fewer parts, simpler exhaust piping, no stuck wastegates, no leaking wastegates, wider range of boost control, no CO2 required and faster reacting boost control.
If you're playing with 2-steps and things, have you had it to a track?
I just started taking it to the track, before I added the two step. Sheared all 5 Moroso studs, shifting to second gear on the second shakedown pass. I believe my lug nuts must have been loose. Car is fine, didn't hit the wall, replaced studs with bigger diameter just in case.
Originally Posted by Forcefed86
So how are you managing to do all that? Can we see the setup??
You can't see the setup because it's all electronic. No moving parts. But I'll explain how it works in my car.
My car is throttle by wire. My transmission is also electronic, being controlled by my DIY 4L80e transmission controller which is also controlling boost (as well as lots of other parts of the car).
Throttle by wire gets info from the gas pedal (2 potentiometers). Imagine that you floor the gas pedal and then watch the boost gauge on your car and when you saw that it was getting close to your target boost, you simply unfloored the pedal just to the right amount so that the boost will be where you want it. Then adjust your foot slightly to maintain the right boost. Very few of us could do that fast enough, but a computer can. It's done all the time for example in limp mode in most modern cars. You floor the pedal, but the computer keeps the throttle open only enough to get you off the highway.
My computer can generate 2 voltages from 0 to 5 volts, just like the 2 potentiometers on the gas pedal. The pedal makes one voltage go from 0 to 5 and the other from 5 to 0v. My generated voltages can override the gas pedals voltages, but only to reduce the throttle.It's physically impossible, no matter what the program does, for my voltages to increase the throttle. So the foot is always in control for increasing throttle, but the computer can, when needed, be in control for reducing throttle input.
As far as the ECM is concerned, it sees 2 voltages. It doesn't know whether they are directly from the pedal or overridden ones from my computer. As long as the 2 voltages are within the correct range of values of a normal pedal, the computer will adjust the throttle accordingly.
I know I'm going to get these questions so I'm going to answer them ahead of time.
Yes, the throttle plate can move that fast. I did a bench test of my GM gold plate. I generated random throttle position instructions and the plate moved so fast, I was almost invisible while moving. For those who think that the electronic throttle is slower than your foot, you are wrong. Wish I had taken a video of that.
No, the feedback loop is not slower than a wastegate. Think about this. In a wastegate setup, a change in boost requires the following sequential steps to happen before the change is corrected.
1) the pressure difference in the manifold has to get through the air hose, usually a small diameter.
2) then the chamber in the wastgate has to be filled (or reduced) with more air so it can affect the spring.
3) the spring now lets the mechanical wastegate valve close (or open) more.
4) the pressure in the exhaust manifold is exhausted through the wastegate valve.
5) the turbine wheel now sees less pressure and begins to decelerate.
6) the compressor wheel slows down and reduces the pressure in the intake manifold.
7) less pressure in the intake manifold means less gasses burned.
If you control the throttle plate instead, you jump directly to step 7. Closing the throttle plate caused less pressure in the intake manifold and less gases burned.
No, I don't put excess force on the throttle plate (risking catastrophic failure). The throttle plate override in my car never reduces the throttle beyond 30% throttle for boost control. So there is always a way for the pressure to equalize. I'm actually more concerned with taking my foot of the gas while under boost, where the throttle plate can close all the way to idle. That is scary. Especially in a stick car, where it happens so often. A blow off valve helps somewhat, but it's still a scary thought.
No, I'm not in business and don't plan to sell anything.
Didn't the F1 indy cars use something similar? But ran an additional adjustable throttle body at the turbo inlet to limit airflow?
They did back in the 80’s when ecu capability’s were a fraction of what they are today. It was just easier for them to control with a throttle ahead of the compressor.
i wonder how this setup compares to a electronic waste gate like slot of the OEMs are moving to? Definitely would reduce the stress on the turbo but still giving you much grater control.
Have tou you ever logged pressure pre throttle to see how high it gets? That’s would be interesting!
DBW blades are fast, no doubt...but there is always a small lag between pedal and blade movements. Imperceptible really.
But even ramping a blade close to open etc...is is easily visible. Logs can show how long it really takes. But they are a great feature.
And it is true that wastegates in general are pretty slow for all of the reasons you say...hence why it's always best for short plumbing, and control solenoids close to the gate etc etc.
Certainly a different way of doing things though. How does it cope for road use, where you simply do not sit at WOT ? and would use a wide range of throttle openings ? Would it not make for strange behaviour or feel for the driver ?
But why worry about "closing" the throttle on boost....just set it so it will never close fully under such circumstances allowing the throttle to become an air bypass anyway ?
I got rid of my BOV a few years ago and just do this
....
But why worry about "closing" the throttle on boost....just set it so it will never close fully under such circumstances allowing the throttle to become an air bypass anyway ?
I got rid of my BOV a few years ago and just do this
This is how the VR30DDTT motor on the new Infiniti Q50/Q60 does it. Even after WOT, they'll slightly hang the TB blade to let air out of the cold side and avoid needing a BOV.
This is how the VR30DDTT motor on the new Infiniti Q50/Q60 does it. Even after WOT, they'll slightly hang the TB blade to let air out of the cold side and avoid needing a BOV.
At high rpm etc it's easy to hang the blade open a bit on "closed throttle"....ie pedal fully released with no side effects. Just makes sense really. Then at lower rpm's allow the blade to close fully or to a normal idle position.
With the "methanol" pressure sensor on the boost pipe pre-blade, I've never seen any pressure spikes to suggest there is anything of concern happening. And yes, the methanol sensor does actually read boost in the pipes when not spraying meth. So dual purpose lol.
The two step is triggered when the brake is pressed hard. A preset high pressure triggers the two step on. The gas pedal gets floored, but the engine RPM (optionally boost) is now controlled by the transmission controller by reducing the throttle opening and maintaining the desired RPM. Once the brake pressure drops to a preset pressure, the throttle plate goes back to normal and the car automatically launches.
How does it cope for road use, where you simply do not sit at WOT ? and would use a wide range of throttle openings ? Would it not make for strange behaviour or feel for the driver ?
Great question.
For any use that is nowhere near the target boost for that gear and diving mode, there is no override and therefore no difference whatsoever from normal feel. When it approaches the target boost, the plate begins to override so that it has time to react to the boost increase. It terminates the override when the boost drops below a preset delta from the target boost. I can tune all the parameters on how it responds from the touch screen.
For example, in my cruise mode, the 4L80e shifts all 4 gears and lockup. I don't ever want to put boost into my 4th or lockup gears, so the boost target for those two is 0 psi. When I'm accelerating vigorously with some boost and it shifts into 4th, if feels like the parachute opened (well that's an exaggeration).
It's been awfully quiet. Last post in this thread is almost a year ago.
Progress report: Still no wastegate, same engine, same setup, more road miles and way more drag strip events. It's an unconditional success. Besides lots of local and highway driving, I cruise to Island or Atco for an hour and 45, bracket race in the 10s, then cruise home.
Only minor problem I'm having nowadays is keeping the M/T drag radials from spinning on the passenger side rim.
You're closer to Island. Surprised you make the haul all the way south. I'm equally far from both.
Here's a log from last weekend at Atco. Notice the yellow trace (Percent Throttle). The gas pedal is matted to the floor, most of this 10 second ride was hovering around 51% throttle. BTW, my C3 vette weighs 3745.
I may have missed it earlier, but how do you have setup for reaching a boost point? IE, I assume some sort of PID loop for when you begin to approach the target boost? How aggressive is the ramp towards the target and then falling off it to maintain it?
I may have missed it earlier, but how do you have setup for reaching a boost point? IE, I assume some sort of PID loop for when you begin to approach the target boost? How aggressive is the ramp towards the target and then falling off it to maintain it?
Ahhh, a really good question.
The first control method was PID. I don't think I spent enough time tuning it. I dropped it for now. I don't think that the boost (map sensor) signal is smooth enough for a PID. Map sensor is at the end of the manifold and I think it's too variable because of the pulsing inside. I may filter the map sensor or relocate it and go back to pid at some point. I will however go back to pid for launch control of the RPM. RPM signal is much cleaner and I can test that in the driveway. I'm going to use a pre-tested start opening size for the RPM and then let the PID take over from there.
In any case, for now, I have per-calculated the throttle opening for a particular boost level and start the throttle plate closing when I'm 2 psi from the target boost. Boost control shuts off when boost is 5 psi less than the target. That gets the boost pretty close to where I want it. Then I can make small compensations for shifting and for RPM. Found that at higher RPM, needs a little more opening to maintain the same boost.
I plan to test a hybrid PID setup. I'm going to first filter the map sensor heavily, then start boost control by getting to the pre calculated position for that boost, then turn on the PID and let it take over.
There's alot more I want to try, but with the track being so far away, it's a slow slog to perfect it.
08-21-2016, 08:00 AM
I’m 30 minutes from Atco. Between Turnersville and Glassboro. 